St Swithun; hypothesis testing in Winchester

We visited the shrine of St Swithun in Winchester Cathedral. I do like the hypothesis testing element of the St Swithun story. St Swithun's day is July 15th and that was hot in most parts of the country. But it has rained since! However if you read https://en.wikipedia.org/wiki/Swithun you'll see some attempt at scientific reasoning behind the saying based on the position of the jetstream over the UK in mid-July. I do wonder how geographically focused the original saying could have been. Surely no one could have thought it would apply to Wigton, or Australia?? But given the weather in Winchester this year, it hasn't even worked in Swithun's town.

Hosepipe ban: projectile range

The hosepipe ban starts here in 10 days time. I tested the range of a projectile using the hose. In theory, a projectile goes the furthest horizontal distance when aimed at an angle of 45 degrees to the ground. See the top picture for this one. A much bigger angle doesn't fire it as far horizontally. That seems quite easy to understand. Less easy is that it won't go as far at a lower angle. This time the answer is that it doesn't have as far to fall so can't do along as much before it hits the ground.

How high are the stairs?

I tested the altimeter watch by taking readings at the bottom and the top of the Science Block stairs. A height of 7 metres sounds about right and gives a good level of precision for the mountains.

3 dimensions in space at Lancaster University

I liked this corridor of fairy lights at Lancaster. Think of them as stars. Here it is clear that some are further away than others but notice that at the far end of the corridor, they all start to look the same distance away. With space, it is even unclear that any of the stars are close just be using the naked eye. Close stars can have their distance measured by parallax from one side of the Earth's orbit around the Sun to the other side.

Cutting off the electrical supply at Ben Wyvis

I found this under Ben Wyvis. I do see this apparatus quite often on similar lines in different parts of the country. It looks as though you hook the lever and pull. That moves the contacts apart.

No coal at Ferrybridge Power Station

The space behind the bushes used to be a mountain of coal. I was amazed to notice that there was no coal at Ferrybridge power station anymore.

I looked up the new units. https://en.wikipedia.org/wiki/Ferrybridge_power_stations

Turns out that they have put in a multi-fuel power station. This includes biomass and waste. But it is much smaller. The old Ferrybridge was 2GW whilst this new plant is 68MW. That's 30x smaller.

Lapse rate on Barrow

I climbed Barrow on Activities Day. I borrowed a watch with a height readout and measured the temperature at different heights. Here is some of the data

Here is a graph of all of the data:

The temperature falls with height. My data has a gradient of 0.0165 degrees Celsius fall per metre. That's 1.65 degrees Celsius per 100m or 16.5 degrees Celsius per km. The R squared value is low so the data is not that good. The third data point was a clear anomaly. This fall of temperature with height is called the lapse rate. It is explained here https://en.wikipedia.org/wiki/Lapse_rate I need to do more work on the thermodynamics theory but the value I should have got was 9.8 degrees Celsius per 1km so I have a percentage difference of nearly 70%. I knew we would be climbing quickly so that should have eliminated the time of day factor of solar heating and it was dull all morning.

Well handle at Carlisle Castle

On this well handle, the length of the handle is 4x the radius of the drum around which the chain is wrapped. This means that the effort will be a quarter of the load. The density of water is 1 gram per cubic centimetre so a litre of water has a mass of 1kg and a weight of 10N. I might be able to lift 10kg so that I could pull 40kg of water up from the well.

A bigger keg stays colder for longer

I spotted this keg of beer at an event at the weekend. What is the advantage of having one large keg versus the same amount in individual bottles? The large amount will have a smaller surface area and since thermal energy crosses the boundary through the surface, it will take longer to get energy in. Also, since energy required is proportional to mass, the larger mass will mean more energy is needed to produce the same temperature rise.

Heatwave 2: car thermometers

The temperature shown above is quite low but we've been noticing some interesting readings whilst out and about. The main car park in Wigton recorded particularly high temperatures. Concrete has a high specific heat capacity so once it has absorbed thermal energy, it remains hot for a long time, warming the air above it. This was coupled with a metre high wall behind the car park which stopped the breeze shifting the warm air. I have read that the thermometers are placed in different places in different cars. Some are low down in front of the radiator. They can even be in with the wing mirrors. From what I've seen, I would suspect the former for our car.

Flow rate: estimating the numbers at the Oxford Race for Life

We were supporting at the Race for Life and were debating the number of participants. I timed a minute and counted the number of rows of runners who went past. Each row was roughly 5 runners wide. About 60 rows went past - so about one per second. That's 300 runners a minute. It went on for 10 minutes which means 3000 runners. The next day the Oxford Mail was saying "more than 2500" so it turned out to be a reasonable method.

Echo chamber: Carlisle Castle dungeon

It was a lot cooler down in the dungeon. Sound took up to 2 seconds to die away. The reverberation was incredible. Sound must repeatedly bounce from wall to wall with little attenuation each time due to the hard surface. We thought that perhaps the arched roof helped to focus sound waves. I estimated height and width of about 6 m. At 330 m/s the sound would take about 0.02 seconds to go from one side the other so there could be up to 100 reflections before it dies away. I tried humming at different frequencies. There was definitely a resonance at a low frequency. The lowest a human can hear is about 20 Hz. The fundamental mode (1st harmonic) for a 6m chamber would have a wavelength of 12 m. So frequency = wave speed/wavelength = 330/12 = 27.5 Hz. Sounds feasible.

Heatwave part 1: railway speed restrictions

We've been enjoying the most amazing spell of weather for the far north of England but trains in the Carlisle area have been experiencing speed restrictions because the line have been warped by the heat. I have always understood that they leave expansion gaps between rails to cope with the expansion of metal in warm weather. This is why trains traditionally go clickety-clack. But it appears that there has been some warping between the joints, hence the speed restrictions. But they have also been painting the rails white in places to reduce the absorption of infra-red from the Sun. I found https://www.networkrail.co.uk/running-the-railway/looking-after-the-railway/delays-explained/buckled-rail/ This suggests that modern rails are made from different bits welded together. I'm wondering if that means the expansions work against each other. Needs some research.

Thinking about the green flash

It has been a brilliant week for sunsets. As light from the Sun passes into and through the atmosphere, it slows down slightly and is bent. This bending depends on the optical density of the air (its refractive index) and varies with the density of the air layers. We could draw a diagram in which light from the Sun was unbent and traveled straight. Then we could work out when it was below the horizon and we could no longer see it. However, because of refraction and the bending, straight line rules don't work and the top of the Sun would still just be visible. This hair-splitting depends on how you choose to define "over the horizon". So in my last picture, I can argue that the Sun is actually over the horizon. At this last point, the refraction splits the light into colours as does a prism. The last colour to be seen should be blue but that is selectively scattered leaving the last colour as a green flash in perfect conditions. I thought I caught a glimpse. I am finding the explanations hard going so expect more when I've done more thinking.

Melting point of bitumen - road in Wasdale

The asphalt has melted on the roads in Cumbria! It's wonderful that the weather is so hot. They have sent the salt gritters out to spread road stone on the bitumen. Bitumen has a high melting point because it is made of long, heavy molecules. I think that this means that there can be more intermolecular forces to hold the molecules together in a solid formation. More joins to separate means more themral energy needed so higher temperature. The explanations usually focus on higher boiling points. I haven't seen one that explains melting points.